1. Field of the Invention
This invention relates to a cassette type gas cylinder containing liquefied fuel gas and a manufacturing method thereof and, more particularly, a structure which enables an alarm for the volume of remaining gas to be given.
2. Description of the Prior Art
Portable heaters are heretofore widely known wherein combustion is effected by gas supplied from a cassette gas cylinder set into a portable heater containing liquefied fuel gas instead of gas supplied through a gas hose connected to a gas outlet of town gas. This cassette type gas cylinder is used with portable heaters and stoves for outdoor activity purposes or with other types of gas apparatuses.
The above-mentioned cassette type gas cylinder is provided with a cylindrical container body, and a valve for opening and closing the discharge of liquefied gas contained in the container. This container is set into a gas apparatus while being laid. A nick-shaped indentation which engages with a corresponding protuberance of the gas apparatus is formed on the end of the container so that a definite position of the container can be directed to the upper side. A gas flow guide channel extends from the inner end of the valve into an upper space inside the container body defined when the container is positioned horizontally, and the upper end of the channel is open in the upper space. This ensures that vaporized gas is constantly given off from a gas space, which in turn prevents the supply of liquefied fuel as it is.
However, in the case of the gas cylinder of the above-mentioned type, it is difficult to know the volume of remaining gas from the outside when the amount of liquefied fuel gas contained is reduced as a result of its use. Also, a gas spray velocity tends to drop sharply, and hence there is a fear of unforeseeable consumption of fuel which causes the gas to be extinguished.
In other words, the volume of the remaining fuel of the cassette gas cylinder can be definitely ascertained by removably swinging the container away from the gas apparatus. Accordingly, an opportunity for replacing the gas cylinder with a new one is difficult to realize while the gas cylinder is set in the gas apparatus, and the fuel may come to an end without the preparation of a spare gas cylinder. Hence, there is a demand for an alarm which is sounded when the volume of the remaining fuel is reduced to a nominal amount.
When the reduction of the remaining fuel is informed by sounding an alarm, there arises a problem that such an alarm is not clearly noticed because sound produced inside a sealed container tends not to travel very well to the outside. The use of a battery for providing an alarm built into the gas cylinder adds to the cost of the gas cylinder, and such an alarm may be erroneously sounded while the gas cylinder is being transferred.
Further, when a remaining volume alarm unit is disposed inside a cassette type gas cylinder, it is necessary to arrange a compact remaining volume alarm unit in an limited internal space of the cylinder, and to ensure a superior assembly property of the gas cylinder.
Moreover, the container of the cassette gas cylinder is constituted by: joining a circular top to the edge of a circular container body; connecting a lid to which a valve is fixed to the center aperture of this top, so that the top is built up; and filling the container with liquefied gas. When a remaining volume alarm unit is built into the cylinder, the remaining volume alarm unit integrated with the valve of the lid must be inserted into the aperture of the top. This narrow aperture makes it difficult to insert the alarm unit, which in turn causes the mounting characteristic of the alarm unit to be deteriorated, thereby leading to a drop in productivity.